Tubing.



E. T. GREENFIELD.

TUBING.

APPLIOATIOKIILED OUT. 3, 1908.

938,575. Patented Nov. 2, 1909.

WITNESS UNTTED STATES PATENT OFFICE.

EDWIN :r. eanmmmtli, or xumnsna, YORK- specification of Letters Patent,

Patented Nov. '2, .1909.

I l pplimtiog filed Octoher a, 19cc. Serial 110.456.1176.

To all whom it may Be it known that I,EDWIN T. 'GREENFIELD,

a citizen of the United States, residing at Kiamesha," in the county of Sullivan and State of New York, have invented a certain new and useful Improvement in Tubing, of which the followin is a specification.

This invention r ates to tubing consistin of spirally-formed strip-metal, and-has re "erenee more particularly to such tubing when used as armoring for electric conductors.

in buildings, itis frequently necessary to remove the armoring -from the conductors along a portion of the length of the conductors, as, for instance, in baring the end of known as stripping but .at the other en the armorin cannot be so stripped, since the end spira is held inplaee by the underla in portion thereof which underlies the e go 0% the nextadjacent spiral. The armar-in at this end-oi. a conductor has'sometimes nremoved by cutting .the armoring at the desired point, as, for, instance, by

ineanso-f a 'hack saw, and then unwinding it fronithis out to the end; butthis practice has been strongly condemned, because of thedan' r of breakingand possibly cross-connecti the conductors, by t- 'saw'passing throng the insulation and ngaging the conductors. 1

The objeetof my invention is to provide Y .an 'armonngso constructed that it may be readil removed at either end of a conduce' tor without danger of injury to the conduc tors, and this without appreciably reducing the strength of the armoring.

In accordance wi the invention, I pro- '1 -vide weakened portions in the strip emthrou ployed for the armoring, at intervals out its length, such that the comple aimoring may be readil severed at these portions and t e armoring unwound from the point where it is thus severed. .The weakened portions may be cute passing entinelythrough the strip at In installing armored electric conductors indented, such indentations being of saidcient depth to permit of readily rupturing the strip along the line of the indentation. The strip thus weakened at one, edge thereof only; that is, at the edge which forms the underlapping portion of the spirals; preferably, it extends a slight dis- .tance farther than ,this underlapping portion of the strip, so that the positions of the weakened portions may be readily detected from the exterior of the tubing.

I have illustrated the preferred embodiment of my invention in the accompanying drawings, in which-- Figure 1 is a sectional elevation of a length-of armored conductor, F i 2 is a sec-.

one edge thereof, or the strip may be merely tion of a portion of the armori-ng thereof,

and Fig. 3 is a bottom View of a portion of the strip of the armoring.

'Referring to these drawings, 1 indicates i van insulated electric conductor, provided with an armoring -2, consisting of a' strip of sheet-metal curved transversely and thenwound spirally so as to form a series of spirals each interloc i with and movable relatively to the spira s adjacent thereto. In forming the armoring, a asket 3 may be led in between adjacent spira The lateral curvature which the strip is given ma be varied as desired, though that which I ave shown is well adapted for th-isuse. In the drawings, the stri is shown as provided with a central over app'ing portion 4, an extension 5 at the edge of this portion, an underlapping portion 6 at the op site edge of the overlap iaig portion 4, an a flange 7 at the edge 9 the-underlappin When a strip thus curved laterafiy is formed into a series of .convolutions, the adjacent convolutions may move one relatively to ,another and will be interlocked 8X- eesslve movement by the coaction of the flanges 7 with the flanges at the junction of the central portion 4 and extension '5.

portion 6.. I

Before spiraling the strip,-I provide'weakened portions therein at mtervalsthroughout the length of the strip. These weakened portions may extend entirely across the strip, but I prefer to make them they extend only across that part of the strip which forms the underlappmg portions of the spirals, or a little in excess of-this so that the weakened portions extend a short ofsuch size that 1 distance into the part of the strip which forms the central or overlapping portion.

The weakened portions may be formed in various ways, as by cuttinglentirely through the metal at oneedge of t e strip or by mdenting the metal along a line extending transversel of the strip, such indentation extending ut a portion of the way through the strip. In the drawings, I have shown a combination of these two methods of providing the weakened portions,.the strip being cut entirely through at its underlapping-v indented on its under 7 edge 'as shown at 8 an si e from this cut over a slight distance into the central or overlapping portion 4 as shown at 9. The position of the indentation shows on the exterior of the armoring or the outer side of the strip as a low ridge is formed along the line of the indentation or the surface of the metal is scoredby the blow which formed the indentation on the opposite side. The spacing of the indentations along the strip may be varied as desired; in practice, I find it suflicient to so space them that every alternate spiral has a weakened portion therein as shown in Fig. 2. With armoring thus formed, the removal of the armorin from a length of the conductor may be rea. ily accomplished without danger of injury to the conductors. The position of the weakened portion nearest the point at which it is desired to sever the armoring may be easily seen on the surface of the-overlapping portion 4. -From the end of this weakened portion to the edged the strip at the flange 5, the metal may be readily severed, as by means of a hack-saw, without danger of injury to the conductors since the conductors are protected whilemaking this cut by the underlapping portion of the next adjacent spiral which underlies the cut. This being done, the strip is severed or the remaining portion thereofmay readily be severed because it has been so weakened by the indentation and the armoring may be stripped by unwinding it from the cut back to the desired point.

Having now described mylinvention, what I claim as new therein and desire to, secure by Letters Patent is as follows 1. A tubing consisting of a single strip of sheet-metal spirally formed with a portion edge thereof weakened at intervals metal formed spirally with each convolution overlappin andinterlocking with the con volution a j acent thereto, the strip for said tubing being weakened at intervals, substantially as set forth.

'4. tubin 'consistin formed spirally with eac ping and interlocking with the convolution of strip metal conv olutign lapadjacent thereto, the underlapping portions of certain of the convolutions bein cut or weakened so. that they may be rea 11y ruptured, substantially as set forth.

5. A tubin consistin ping and interlocking with the corryolution adjacent thereto, the underlapping portions of-certain of the convolutions belng cut or weakened so that they may be readily ru tured and the ppsitions of saidcuts or weakened port-ions eing indicatedupon the ex terior of the tubing, substantially as set forth.

6. A tubin consisting of a strip of sheetmetal forme spirally with one edge of each convolutibn overlapping and the other underlapping the edges of the adjacent s irals,

said strip being cut orkweakened'so t at it may be readily ru tured at intervals from its underlapping edge to a point bey overlap ing edge of the adjacent splral, sub,- stantial y as set forth.

7. A tubing consisting of a sheet-metal strip curved transversely and wound spirally to form a series of interlockin relatively movable convolutions, the un erlap- P being cut or weakened and the overlapping portions being marked-to indicate the positions of said cuts or weakened points, sub-,

stantially as set forth.

of strip metal formed spiral y with eac convolution lap 0nd the portions of certain of'said convolutions 8. A tubing consisting of a sheet-metal strip curved transversely and wound spirally to form a series of interlocking, relatively movable convolutions, certain 'of said convolutions being cut orfweakened and said cuts or weakened points extendingacross the.

underlapping portions and a part of the overlapping substantial y as set forth.

9. A tubing consisting of a sheet-metal strip curved transversely and wound spirally to form a series of interlocking convolutions each underlapping at one edge thereofthe next adjacent spiral, said strip having weakened portions therein at intervals extending from the underlapping edge of a spiral transversely of the strip to a point adportions of said convolutions,

j acent to the underlapping edge of thenext adjacent spiral, substantially as setforth. This specification signed and witnessed this 28thday of Sep., 1908.

Witnesses:

WM. T. RUETE, HARRY H. HORNSBY.

EDWIN T.GREENFIEL D. 7 

